The last piece of log, has been recently posted, because I've just found it. It seems Java process do something and began to slowly eat all the resources of the server. I don't know exactly if this could be the root cause.

Well, what have you tried? When anything electronic spontaneously shuts down, high temperature is one aspect you should check.
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SandokanDec 11 '12 at 8:32

No, it doesnt shut down, it hangsup. I need to hardreset it. Could be a failing core of the cpu? it has a opteron 4 core.
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PsySkeletorDec 11 '12 at 9:11

Anything related about that point in time? Some Cron job running causing a lot of I/O or memory usage that may be related? And what do you mean by "freezes up always at night"? 125983 / 60 / 60 = 35 hours of uptime.
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gertvdijkDec 11 '12 at 10:20

2

Have you given it a dose of memtest86? Have you tried unloading some of the unneeded kernel modules (for a debian server this box has an awful lot of stuff loaded that a server never needs...)? Try setting up a cronjob a few minutes before the "scheduled" crash that dumps pstree -pa , uptime, the contents of /proc/[useful things - slabinfo, meminfo, interrupts....] , ... into a file (sync!) or email... Also, why are there tainted kernel modules on a server (manually compiled stuff that might have been built with a mismatched compiler?)
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rackandbonemanDec 11 '12 at 12:11

I edited original question with new data i found. @rackandboneman I don have idea, i took this server 4 months ago and it was running and deeply config. At the beggining we tought it was a hardware problem, but this sunday we changed the motherboard and 35 hours later crashed again.@gertvdijk there's only a cronjobs for backups and at 01:00 a ntp update. Nothing more.
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PsySkeletorDec 11 '12 at 12:35

Thanks, i didnt know hat about B on trace calls, nice to know. Today we have programmed a maintenance on the server to change RAM. I will keep you fellows updated. Thanks!
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PsySkeletorDec 12 '12 at 15:10

Thanks, but its impossible, its on a hosting and it costs a lot to do : open kvm, do backup, reinstall. Impossible at all. But really, thanks.
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PsySkeletorDec 12 '12 at 15:09

If the hardware is not yours then you should pretend them to check and fix it for free. If the problem lies in the software (corrupt fs / files) then it's your problem, reinstalling would be expansive and yield a sane production server, fixing file-by-file could make it work more or less but I wouldn't ever call it production-ready.
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Luke404Dec 12 '12 at 17:04